結果

問題 No.1976 Cut then Connect
ユーザー tamatotamato
提出日時 2022-06-10 23:30:52
言語 PyPy3
(7.3.15)
結果
RE  
実行時間 -
コード長 3,539 bytes
コンパイル時間 157 ms
コンパイル使用メモリ 82,560 KB
実行使用メモリ 131,816 KB
最終ジャッジ日時 2024-09-21 06:58:38
合計ジャッジ時間 7,146 ms
ジャッジサーバーID
（参考情報） 		judge3 / judge2
このコードへのチャレンジ
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テストケース

テストケース表示
入力 結果 実行時間
実行使用メモリ
testcase_00 AC 42 ms
54,272 KB
testcase_01 RE -
testcase_02 RE -
testcase_03 AC 209 ms
98,432 KB
testcase_04 RE -
testcase_05 RE -
testcase_06 WA -
testcase_07 RE -
testcase_08 RE -
testcase_09 AC 275 ms
108,260 KB
testcase_10 RE -
testcase_11 WA -
testcase_12 WA -
testcase_13 RE -
testcase_14 AC 253 ms
102,272 KB
testcase_15 RE -
testcase_16 WA -
testcase_17 WA -
testcase_18 WA -
testcase_19 RE -
testcase_20 AC 341 ms
125,496 KB
testcase_21 AC 244 ms
105,880 KB
testcase_22 RE -
testcase_23 AC 42 ms
54,704 KB
testcase_24 AC 42 ms
54,272 KB
testcase_25 AC 41 ms
54,400 KB
testcase_26 AC 43 ms
54,400 KB
testcase_27 AC 44 ms
54,440 KB
testcase_28 RE -
testcase_29 WA -
testcase_30 RE -
testcase_31 RE -
testcase_32 AC 43 ms
54,272 KB
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ソースコード

diff # 

mod = 998244353


def main():
    import sys
    from collections import deque
    input = sys.stdin.readline

    def radius(v0, v1):
        que = deque()
        que.append(v0)
        seen = {}
        seen[v0] = 0
        v_last = 0
        while que:
            v = que.popleft()
            for u in adj[v]:
                if u == v1:
                    continue
                if u not in seen:
                    seen[u] = seen[v] + 1
                    que.append(u)
            v_last = v
        v0 = v_last
        que = deque()
        que.append(v0)
        seen = {}
        seen[v0] = 0
        v_last = 0
        while que:
            v = que.popleft()
            for u in adj[v]:
                if u == v1:
                    continue
                if u not in seen:
                    seen[u] = seen[v] + 1
                    que.append(u)
            v_last = v
        return seen[v_last]

    N = int(input())
    adj = [[] for _ in range(N + 1)]
    for _ in range(N - 1):
        a, b = map(int, input().split())
        adj[a].append(b)
        adj[b].append(a)

    que = deque()
    que.append(1)
    seen = [-1] * (N+1)
    seen[1] = 0
    par = [0] * (N+1)
    child = [[] for _ in range(N+1)]
    seq = []
    while que:
        v = que.popleft()
        seq.append(v)
        for u in adj[v]:
            if seen[u] == -1:
                seen[u] = seen[v] + 1
                par[u] = v
                child[v].append(u)
                que.append(u)
    seq.reverse()

    v0 = seq[0]
    que = deque()
    que.append(v0)
    seen = [-1] * (N+1)
    seen[v0] = 0
    par = [0] * (N+1)
    child = [[] for _ in range(N+1)]
    seq = []
    while que:
        v = que.popleft()
        seq.append(v)
        for u in adj[v]:
            if seen[u] == -1:
                seen[u] = seen[v] + 1
                par[u] = v
                child[v].append(u)
                que.append(u)
    seq.reverse()

    v1 = seq[0]
    D = seen[v1]
    if D & 1:
        v = v1
        for _ in range(D // 2):
            v = par[v]
        vl = v
        vr = par[v]

        dl = radius(vl, vr)
        dr = radius(vr, vl)

        print(max((dl + 1) // 2 + (dr + 1) // 2 + 1, dl, dr))
        assert False
    else:
        ans = N * 2
        v = v1
        for _ in range(D // 2):
            v = par[v]
        v0 = v
        que = deque()
        que.append(v0)
        seen = [-1] * (N+1)
        seen[v0] = 0
        par = [0] * (N+1)
        child = [[] for _ in range(N+1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if seen[u] == -1:
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()

        subtree_len = [(0, 0)]
        for c in child[v0]:
            que = deque()
            seq = []
            que.append(c)
            while que:
                v = que.popleft()
                for vv in child[v]:
                    que.append(vv)
                seq.append(v)
            subtree_len.append((seen[seq[-1]], c))
        subtree_len.sort(key=lambda x: x[0], reverse=True)

        d1, d2, d3 = subtree_len[0][0], subtree_len[1][0], subtree_len[2][0]
        d23 = d2 + d3
        d123 = (d23 + 1) // 2 + (d1 - d3) + 1
        if d123 <= d23:
            print(d23)
        else:
            print(((d1 + d2) * 2 - 1) // 3 + 1)


if __name__ == '__main__':
    main()
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